Macroalgae as a tool for assessing the ecological status of coral reefs under the Water Framework Directive: A case study on the reef flats of La Réunion (Indian Ocean)

Influence of Freshwater Discharges on Biogeochemistry and Benthic Communities of a Coral Reef Ecosystem (La Réunion Island, Indian Ocean)

“…Since the 1980s, it has been observed a degradation of La Saline ecosystem through a constant decrease in the living coral cover correlated with a raise in algal cover in the reef flat zone and on the outer reef slope (Ahamada et al, 2008;Naïm et al, 2013;Zubia et al, 2018;Nicet et al, 2019). Although varying spatially and seasonally (Cuet et al, 2011;Naïm et al, 2013), algal cover overall has displayed a substantial increase since the late 1990s in La Saline fringing reef (Tourrand et al, 2013).…”

“…Groundwater is generally enriched in dissolved nitrogen (mainly nitrates) relative to phosphorus, displaying high N/P ratios (Slomp and Van Cappellen, 2004;Street et al, 2008;Santos et al, 2013;McMahon and Santos, 2017). Because reef waters are often oligotrophic and N-limited, SGD may lead to their eutrophication, which is characterized by the shift from corals to algal communities (Koop et al, 2001;Dailer et al, 2010;Zubia et al, 2018).…”

“…SGD from volcanic aquifer has been shown to be the main source of freshwater to La Saline reef (Join et al, 1988) and to enrich its waters with nitrates derived from anthropogenic sources (Cuet et al, 1988;Naïm, 1993;Mioche and Cuet, 1999). Several studies have been conducted so far on this ecosystem to determine the effects of SGD/eutrophication on C, N, P, and O fluxes (Clavier et al, 2008;Cuet et al, 2011;L'Helguen et al, 2014), the distribution of FDOM and hydrocarbons (Tedetti et al, 2011;Guigue et al, 2015), the rates of bioerosion (grazers/borers) and calcification (corals) (Chazottes et al, 2002;Chauvin et al, 2011), and the distribution of coral and algal communities (Tourrand et al, 2013;Zubia et al, 2018). Nevertheless, since most of these works have focused on quite limited geographical (back reef) areas of the reef, the distribution of chemical and biological parameters at a larger spatial scale (from back to fore reef waters, from north to south of the reef) has not been evaluated yet.…”

Macroalgal diversity for sustainable biotechnological development in French tropical overseas territories

“…data) and another single one for the Scattered Islands (i.e. Gloriosos, Juan De Nova and Europa; Mattio et al 2016), whereas many studies on algal composition have been made recently in Reunion Island (Ballesteros 1994, Zubia et al 2018. The diversity of macroalgae varies in accordance with the habitat diversity and the surface of each territory, but also depends on the sampling effort and that had varied with the territory.…”

“…The development of high-performance molecular tools now makes it possible to improve species identification or delimitation in different ways. Molecular analyses Payri 1985, Ballesteros 1994, Zubia et al 2018. Scattered Islands: Mattio et al 2016.…”